Determining the quantities of gases dissolved in a liquid

ABSTRACT

The invention relates to a new method for determining the content quantities, solubilities and/or saturated vapor pressures of gases dissolved in a liquid, which is characterized in that in order selectively to determine the individual content quantities of at least two gases dissolved in the sample liquid, more particularly carbon dioxide, nitrogen and/or oxygen, and/or the solubilities or saturated vapor pressures thereof, the volume of at least one measuring chamber filled with the liquid for testing is increased in at least two steps by volume increase factors differing one from another—each having numerical values greater than 1—, in that, after each of the volume increase steps, the equilibrium pressure establishing in the measuring chamber is ascertained, and in that, on the basis of the at least two measured pressure values obtained in this way, the content quantities of the individual gases dissolved in the liquid, and/or the solubility or saturated vapor pressure thereof are calculated individually.  
     It also relates to several variants of a device for implementing the analysis method.

[0001] The present invention relates to a method and also a device for selectively determining the content quantities of gases, such as carbon dioxide, nitrogen and/or oxygen, for example, dissolved in liquids, more particularly beverages, and also for ascertaining the solubility (solubilities) and/or saturated vapour pressure(s) thereof in the said liquids.

[0002] The main emphasis of the invention is the determination of the content quantities of gases dissolving ii liquids or dissolved in the same in fairly large quantities. However, as well as the content quantities of more than one gas dissolved in a liquid which is of prime interest here, it should also be possible to determine the solubility (solubilities) and/or the saturated vapour pressure(s) of an individual gas or of several gases in the liquid.

[0003] Constituting a further essential subject of the invention is a device in the form of various design variants for determining content quantities, solubility (solubilities) and/or saturated vapour pressure(s) of at least one gas, but preferably at least two or more gases, in a liquid containing the said gas or gases dissolved therein, the main emphasis being the implementation of the new determination method just referred to.

[0004] A considerable number of often quite different methods and devices for determining the content quantities of gases dissolved in liquids, such as carbon dioxide in particular, have become well known and also commercially available. Some of these known methods and devices are in principle also suitable for determining other gases, such as oxygen and/or nitrogen in particular, dissolved in liquids such as beverages, for example. The characteristic features of these will be briefly described below:

[0005] a) Pressure and Temperature Measurement in a Sealed Measuring Chamber Expanded Once:

[0006] A representative sample of the liquid for measuring is introduced into a measuring chamber. Where measurements are performed on casks of beverages. the whole cask often serves as the measuring chamber. After the measuring chamber has been closed, the liquid sample to be analysed is expanded by increasing the volume of the measuring chamber, e.g. by means of a sort of piston-type injector fitted fluid-tight to the said chamber, or, where measuring is being implemented in the beverage cask, by means of a short release of pressure. The pressure establishing after the expansion and the sample temperature are then measured. The carbon dioxide content is then calculated from these in accordance with Henry's law. Other gases dissolved in the sample liquid, such as oxygen and nitrogen in particular, affect the ascertained carbon dioxide content. Commercially available devices differ from one another by, among other things, the method of sampling, the shape of the measuring chamber, and by differing measures for the accelerated establishment of equilibrium pressure after the expansion or for extrapolating the equilibrium pressure.

[0007] b) Measurement in a Liquid-Free Measuring Chamber Separated by a Gas-Permeable Membrane:

[0008] A membrane substantially permeable only to carbon dioxide separates a measuring chamber from the sample liquid. The measuring chamber is periodically evacuated or flushed with a reference gas. The carbon dioxide content or its variation over time in the measuring chamber is then ascertained by measuring pressure, thermal conductivity or infrared absorption and in addition temperature, and from these the carbon dioxide content of the liquid is then calculated.

[0009] c) Measurement in a Liquid-Filled Measuring Chamber Separated by a Gas-Permeable Membrane:

[0010] A membrane substantially permeable only to carbon dioxide separates a measuring chamber filled with a suitable liquid from the liquid for analysis. As a result of absorbing the carbon dioxide permeating through the membrane, the liquid in the measuring chamber changes, e.g. in its pH value which is measured together with the temperature, from which the carbon dioxide content of the liquid to be analysed for the said carbon dioxide content can then be calculated.

[0011] d) Direct Infrared Absorption Measurement:

[0012] By means of infrared absorption measurements, usually in the mid infrared range, performed on the liquid to be analysed, or sample liquid, the carbon dioxide content in the liquid is directly determined.

[0013] e) Wet Chemical Analysis:

[0014] In a defined sample volume, by means of the addition of appropriate chemicals the dissolved carbon dioxide is absorbed, separated out, and determined gravimetrically or titrimetrically.

[0015] In d) and e) the carbon dioxide content is directly determined, in a)-c) the saturated vapour pee of the carbon dioxide in the liquid for analysis is primarily ascertained. Wit the solubility of the carbon dioxide in the liquid for analysis taken as known, assumed or only estimated, the carbon dioxide content of this liquid is calculated from the saturated vapour pressure ascertained directly or indirectly. Since in practice the solubility of a gas in an aqueous solution other than pure water is always known only approximately at most, a problem arises from this if the results of different methods are compared with one another.

[0016] The actual invention is based in particular on the group of methods and devices described above under a) which are based on pressure and temperature measurements in a sealed measuring chamber which has been expanded in a defined manner in only one step.

[0017] The subject of the present invention is a new method for determining the content quantities of gases dissolved in a liquid, preferably a beverage, wherein, after a measuring chamber equipped at least with a pressure-measuring sensor has been filled completely with the liquid to be tested for its gas content (the “sample liquid”), and after the measuring chamber has been closed fluid-tight, the volume thereof is increased—staring from a standard volume—by a predetermined factor, and the equilibrium pressure establishing thereafter in the measuring chamber is ascertained, and—based on the measured pressure value obtained in this way—the gas content of the liquid for analysis is calculated, the said method being characterised in that

[0018] in order selectively to determine the individual content quantities of at least two or more gases, more particularly carbon dioxide, nitrogen and/or oxygen, differing from one another in their solubilities and dissolved in the sample liquid, and/or the solubilities and/or the saturated vapour pressures of the gases

[0019] in at least two or more steps corresponding at least to the number of gases dissolved in the liquid and to be tested for their content quantities,

[0020] the volume of at least one measuring chamber filled with the sample liquid is increased, starting from the standard measuring chamber volume, by volume increase factors differing from one another—each having numerical values greater than 1,

[0021] in that, after each of the volume increase steps, the equilibrium pressure establishing in each case in the measuring chamber is ascertained, and

[0022] in that, on the basis and with the inclusion of the at least two or more than two measured pressure values obtained in this way,

[0023] the content quantities of the individual gases contained or dissolved in the liquid, and optionally the solubility and/or the saturated vapour pressure of at least one of the gases in the said sample liquid, are calculated individually.

[0024] The new method has the following new features which are extremely important for commercial application, and offers in particular the following advantages:

[0025] The effect of other gases dissolved in the sample liquid on the ascertained gas content, i.e. the carbon dioxide content, for example, is minimized. In preferred embodiments the effect of each of the other dissolved gases can be eliminated, so that the content quantities of other gases dissolved in the sample liquid, such as oxygen and nitrogen, can also be determined.

[0026] The actual solubilities and/or saturated vapour pressures of the individual gases dissolved in the sample liquid may additionally be ascertained and thus the content quantities of these gases can be determined exactly, although their solubility in the actual sample liquid, other than pure water, is not known.

[0027] The method according to the invention is characterised, amongst other things, in particular in that, for example, the effect of other dissolved gases, i.e. other than CO₂, for instance, on the carbon dioxide content of the sample liquid ascertained in the particular case can be eliminated, and in that optionally the content quantities of the other gases dissolved in the sample liquid, and also the actual solubilities of each individual one of these gases in the sample liquid, can be determined as well.

[0028] Along with the main component, carbon dioxide, already repeatedly mentioned above, oxygen and nitrogen are the “other” important gases dissolved in beverages or similar liquids to which gas content measurements are applicable. The solubilities of carbon dioxide, oxygen and nitrogen in aqueous solutions differ considerably from one another.

[0029] If the sample of liquid, abbreviated to sample liquid, is expanded in the sealed measuring chamber, a liquid and a gas phase form from the original single liquid phase in which all the gases are dissolved. Because of the very different solubilities of the gases in the sample liquid, the proportion of the partial pressures of the individual gases in the gas phase differs substantially from the proportion of the saturated vapour pressures of the dissolved gases in the original, i.e. pre-expansion, sample liquid. The general principle is that the lower the solubility of a gas in a liquid is, the more the partial pressure of the said gas dissolved in the liquid decreases when the volume is increased.

[0030] Thus in the method according to the invention—specifically to determine the content quantities of at least two gases dissolved in the sample liquid—at least two or more than two volume increase steps are implemented in each case. After each of these volume increase steps, the equilibrium pressure then establishing and advantageously also the temperature prevailing at the time are each measured. From the values ascertained are calculated the content quantities and, if required, also the solubilities and/or saturated vapour pressures of the individual gas components differing from each other in their individual solubilities.

[0031] The basic algorithms used within the scope of the present invention—to calculate content quantities, and also solubilities and saturated vapour pressures, and thus for simpler cases—are explained with the aid of the following calculation example which describes in general terms and in actual numbers the method of calculation—representing a component part of the invention:

[0032] Calculation example for a beverage, such as beer for example, which exists as a liquid phase enriched by carbon dioxide and nitrogen: Solubilities L at a specific L(CO₂) = 1.058 bar¹ L(N₂) = 0.017 bar¹ measuring temperature: Saturated vapour pressures: pCO₂ = 2.50 bar pN₂ = 2.00 bar

[0033] As a result of a volume increase, on the basis of Henry's and Boyle's laws the following partial pressures occur in the gas phase: p′ = p/(1 + k/(L*p_(s))) p′ partial pressure of a gas after the measuring chamber volume increase p original saturated vapour pressure of the gas in the liquid k volume increase factor L solubility of the gas in the sample liquid p_(s) standard pressure (1 bar)

[0034] Volume increase of 3% and 10% k₁ = 0.03 k₂ = 0.10 respectively: p′CO₂ = 2.431 bar p′CO₂ = 2.284 bar P′N₂ = 0.723 bar P′N₂ = 0.291 bar Measured pressure (= p′CO₂ + P₁ = 3.154 bar p₂ = 2.575 bar p′N₂):

[0035] From the equilibrium pressures p₁ and p₂ measured after the two volume increases k₁ and k₂ to be implemented according to the invention, the original saturated vapour pressures pX and pY of two dissolved gases with known solubilities L(X) and L(Y) are calculated with the aid of the following linear equation system:

p ₁ =pX/(1+k ₁/(L(X)*p _(s)))+pY/(1+k ₁/(L(Y)*p _(s)))

p ₂ =pX/(1+k ₂(L(X)*p _(s)))+pY/(1+k ₂/(L(Y)*p _(s)))

[0036] This equation system is to be solved according to pX and pY.

[0037] When the numerical values L(CO₂)=1.058, L(N₂)=0.017, k₁=0.03, k₂=0.10, p_(s)=1 given in this example are used and the equation system is solved according to pX(=pCO₂) and pY(=pN₂), the following equations result for pCO₂ and pN₂:

pCO ₂=−0.7681*p ₁+1.9120*p ₂ (=2.50 bar for p₁=3.154 and p₂=2.575 bar)

pN ₂=4.8297*p ₁−5.1405*p ₂ (=2.00 bar for p₁=3.154 and p₂=2.575 bar)

[0038] Multiplying the calculated saturated vapour pressures pCO₂ and pN₂ by the respective gas solubility L(CO₂) or L(N₂) produces the sought gas contents in the sample liquid.

[0039] With the units selected here, the gas contents are produced as “volume of dissolved gas in the standard state per volume of liquid”. This industrially standard unit for the gas content may be converted by means of simple conversion factors into other units, such as “g/L”, for example.

[0040] Optionally the above calculation may be amplified by a correction which eliminates the temperature-dependent vapour pressure of the liquid sample components from the measured pressure values, but this is not set out in detail here.

[0041] Using the two-step or multiple-step method according to the invention, as well as the saturated vapour pressures, the solubilities of carbon dioxide and/or other gases dissolved in the sample liquid may also be determined, as already mentioned quite briefly in the introduction. This is particularly important when the content quantities of several gases dissolved in the sample liquid are to be determined and the solubilities of the individual dissolved gases to be determined in the actual liquid itself are not precisely known. This is very often the case as the rest of the composition of the sample liquid has a strong effect on the solubilities of the gases dissolved therein, e.g. the solubilities of the aforementioned gases in a fruit acid drink are completely different from those of the same gases in pure water.

[0042] In principle it follows that for every unknown quantity—whether this is the gas content and/or the solubility and/or the saturated vapour pressure of individual gas components in the liquid—at least one additional volume increase with subsequent determination of the equilibrium pressure are required for each in any case.

[0043] If there is only one gas dissolved in the sample liquid, the saturated vapour pressure and solubility may be determined as follows from the pressures p₁ and p₂ establishing and measured after two volume increases k₁ and k₂:

L(X)=(p ₁ *k ₁ −p ₂ *k ₂)/(p ₂ −p ₁)/p_(s)

pX=p ₁*(1+k ₁)/(L)(X))*p _(s)

[0044] With the aid of the data for CO₂ from the previous calculation example, the following is obtained:

L(CO ₂)=(2.431*0.03−2.284*0.10)/(2.284−2.431)=1.058bar¹

pCO ₂=2.431*(1+0.03/1.058)=2.50bar

[0045] Where there are several gases dissolved, a corresponding number of volume increase steps and correspondingly more extensive calculation methods are necessary. If more than one gas is dissolved and the solubilities of individual gases are also to be ascertained, non-linear higher-order equation systems result. Their solution is typically achieved iteratively, starting from precise estimated values for the unknown gas solubilities which are as realistic as possible.

[0046] If a gas dissolved in the sample liquid is present in a much greater quantity than all the other gases dissolved therein, and if the solubilities of the other gases are substantially lower and possibly even alike, these other gases may be treed as a single gas component. This is advantageous if, for instance, as well as the carbon dioxide content of a sample, only the air content, for example, is to be determined or if only the effect of all the other dissolved gases on the ascertained carbon dioxide content is to be eliminated. In this case it is possible to use in the equation system for the “hypothetical” solubility of the “other” dissolved gases a weighted mean value of their actual solubilities.

[0047] If, for example, only the content and the solubility of CO₂ as the important main component are sought and oxygen and nitrogen are only dissolved to a minor degree, by means of two accordingly large volume increases, e.g. by 10% and by 20%, the effect of oxygen and nitrogen can also be suppressed to the extent that it can be disregarded and no specific volume increase steps are necessary in order to take it into consideration. Use is made here of the fact that, because of the very low solubilities of oxygen and nitrogen, their partial pressures in the gas phase decrease very markedly as a result of an increased volume increase—as just described—and are no longer significant.

[0048] With regard to the factors of the measuring chamber volume increases advantageously to be observed within the scope of the present invention, according to claim 2 such volume increase factors of between 1.005 and 1.75 have proved advantageous for extreme cases. In some cases these factors may range from 1.01 to 1.50 and in most conventional routine analyses where there is no specific suppression of the effect of other gas components present in small quantities in the sample liquid, volume increase factors of between 1.03 and 1.15, preferably 1.03 to 1.10, have proved successful.

[0049] Since the solubility of gases in liquids generally is dependent to a considerable extent on the temperature, apart from routine measurements with temperature conditions remaining virtually constant, it is preferable, as mentioned in claim 3, to measure the temperature of the sample liquid and include it—if necessary—in the calculations.

[0050] If, as provided according to claim 4, the procedure involves only one measuring chamber in which the preferably at least two volume increase steps are performed one after the other, constancy of the measuring conditions, desired per se, is ensured in a simple manner.

[0051] It has also proved advantageous to employ a variant of the measuring method according to claim 5 in which it is provided that, preferably at the same time, two measuring chambers located slightly apart or adjacent to one another are filled with sample liquid and, again preferably at the same time, the volume increase steps, which differ from each other, are then implemented.

[0052] To achieve the quickest possible establishment of the equilibrium pressures, it is preferred according to claim 6, particularly in the case where a single me g chamber is used, to implement the volume increase steps occurring in chronological succession with gradually increasing volume increase factors in each case.

[0053] If—as already indicated above—only a limited, low number of gases as main components dissolved in the sample liquid or only one gas is determined and the effect of the other gas components dissolved in the liquid are suppressed, it has proved advantageous, as is implied by claim 7, substantially to increase the volume changes in the volume increase steps. If, as already mentioned, these amount to about 1 to 10% in routine analyses, it is advantageous in this design variant, with disregarding of the gases dissolved in small quantities in the sample liquid, to increase the volume increase in at least one of the volume increase steps by a percentage of at least 20%.

[0054] As far as the disregarding referred to above of less significant or unimportant gas components in the sample liquid is concerned, it may be advantageous with respect to these other components, such as air, for example, to assume a “mean” solubility or a mean saturated vapour pressure for them, as may be inferred from claim 8.

[0055] With respect to the way in which the measuring chamber volume increase is brought about, it has already been set out with reference to the prior art that a sort of piston-type injector is used for this, it being important here that fluid-tightness is maintained in every case.

[0056] In the context of the development work for the invention, with regard to the fluid-seating, the mechanical effort, the costs involved, it has proved advantageous to use, instead of a displaceable piston, a defined and reproducibly deformable membrane, made of an elastomer, for example, as is implied by claim 9.

[0057] It should be mentioned at this point that a method of this kind, operating with a volume-increasing membrane, is new as such, and that the use of such a membrane is therefore not limited to a method with a two-step volume increase, but that such a measuring chamber with a membrane is entirely applicable as well to the gas content determining method according to the prior art discussed in the introduction under a).

[0058] It may be particularly advantageous within the scope of the method according to the invention—see claim 10 in this connection—to augment the equilibrium pressure measurements by the addition of selective gas sensors to determine the content of individual gases dissolved in the liquid, and let the results appertaining thereto possibly also be included in the calculation of the content quantities of the other gases.

[0059] Hitherto none of the instruments of the prior art mentioned in the introduction under a) could be described as really satisfactory as fir as establishing the equilibrium gas pressure as quickly and reproducibly as possible after each volume increase step is concerned. In the course of the development of the method according to the invention it has become apparent that generating cavitation in the sample liquid causes the establishing of equilibrium pressure to take place very quickly, in which connection reference is made in detail and with regard to the actual transformation to claim 11.

[0060] In order to achieve the said cavitation effect in the sample liquid located in the measuring chamber, various methods may be used for this, as specified—by no means in fill—in claim 12.

[0061] Here too it should be emphasised that this new method for accelerating the establishing of the equilibrium pressure after each measuring chamber volume increase has taken place is not limited to a two-step volume increase method, but may also be used in the same way in the one-step method according to the prior art.

[0062] It is especially preferred, as disclosed in claim 13, particularly with regard to generating cavitation effects in the sample liquid, to bring about the desired establishment of the equilibrium pressure in the measuring chamber by means of a power-regulated ultrasonic transducer.

[0063] With regard to the introduction of ultrasonic energy, it is advantageous according to claim 14 to adapt the amount thereof to the particular liquid to be analysed for its gas contents, the inclusion of the change over time of the pressure occurring and measured in the measuring chamber after the ultrasonic transducer has been switched off being advantageous as a regulating variable for the ultrasonic power to be introduced into the sample liquid.

[0064] This method vat too may be used both for the one-step volume increase method already previously known and also for the multiple-step volume increase method according to the invention.

[0065] Another essential subject of the present invention is constituted by a new device for selectively determining the content quantity (quantities) and/or solubility (solubilities) and/or saturated vapour pressure(s) of at least one gas dissolved in a liquid, preferably a beverage, according to claim 15, wherein, after a measuring chamber equipped at least with a pressure-measuring sensor has been filled completely with the liquid to be tested for its gas content (the “sample liquid”), and, after the measuring chamber has been closed fluid-tight, the volume thereof is increased at least once by a predetermined volume increase factor and the equilibrium pressure establishing thereafter in the measuring chamber is ascertained, and—based on the measured pressure value obtained in this way—the gas content of the liquid for analysis and/or the solubility of the gas in the said liquid is calculated, in particular for the implementation of the method according to the invention previously described in its various embodiments.

[0066] The new device is characterised in a first preferred embodiment in that it has a fluid-tight measuring chamber which may be filled completely with the sample liquid and closed fluid-tight, comprising at least one partial region of the boundary or wall of its interior space, which partial region is provided for changing the volume of the interior space thereof, is variable in its position and/or surface geometry—while fully retaining the fluid-tightness—and is preferably formed by a membrane, which partial region—starting from a standard position and/or standard geometry—is movable into, and/or deformable to, at least one defined location position and/or surface geometry—producing an increase in the volume of the measuring chamber interior space corresponding in each case to a freely selectable and adjustable volume increase factor.

[0067] If at least two gases dissolved in a liquid are to be selectively determined, as provided in particular in accordance with the method according to the invention previously described in its variants, an embodiment of the device according to claim 16 is preferred.

[0068] Another variant of the device for the purpose previously described is characterised according to claim 17 in that it has at least two measuring chambers, preferably of identical design, adapted for filling completely with the sample liquid and closable fluid-tight, each comprising at least one partial region of the boundary or wall of its restive interior space, which partial region is provided in each case for changing the volume of the interior space thereof, is variable in its position and/or surface geometry while filly retaining the fluid tightness, and is preferably formed by a membrane, each of which partial regions is movable into, and/or deformable to, at least one defined location position and/or surface geometry respectively—producing an increase in the volume of the measuring chamber interior space corresponding in each ease to a freely selectable and adjustable volume increase factor.

[0069] The advantage of his second device variant according to the invention is that, compared with the single chamber measuring method requiting two successive steps of the volume increase and the establishing of equilibrium pressure following each, a two-chamber volume increase method may be implemented in virtually half the time required by the said single chamber measuring method.

[0070] Here again it should be mentioned that the new devices equipped with at least one membrane as the volume-changing element need not be restricted to a two-step or multiple-step volume increase method.

[0071] The two-chamber variant according to claim 18 comprising specifically different measuring chamber volume changes has proved advantageous particularly for implementing the new method, described above in the introduction, for determining the individual content quantities of more than one gas dissolved in a liquid.

[0072] An important requirement for routine measurements is that the time for establishing the equilibrium pressure after each volume increase is kept as short as possible, for which a motion-generating element as described in detail in claim 19, preferably an oscillating body, is preferably used, which sets the sample liquid in cavitation-generating motion or oscillation.

[0073] With regard to the drive of the volume-changing membrane used for the volume-change in the measuring chamber according to the present invention, reference in this connection and with respect to the control of the drive is made to claim 20.

[0074] An embodiment of the new device for determining the content quantities of gases dissolved in liquid and also the solubility (solubilities) and/or saturated vapour pressure(s) thereof according to claim 21 is particularly preferred. The especial advantage of this embodiment of the device is that it can easily be fitted into a liquid vessel and/or a pipeline and in practice on-line or in-line measurements of the gas contents in the liquid, particularly a beverage, located in a vessel and/or flowing in a pipeline, may be undertaken.

[0075] Various advantageous detailed development variants for the embodiment of the new device just described are described in claims 22 to 24:

[0076] The solution according to claim 22 avoids any direct connection between the sample liquid stirring element and the stirrer drive. The embodiment variant according to claim 23 has the advantage that only the sensor surfaces involved in active measurement come into contact with the sample liquid and the other regions or the data-and supply lines of the sensors are completely separate from the fluid space, and this in particular also applies to the embodiment according to claim 24.

[0077] Another embodiment variant, also advantageous and usable for on-line operation virtually without any limitations, forms the subject of claim 25. It essentially comprises a sort of inverse embodiment to the on-line gas content measuring chamber described in the preceding claims 21 to 24.

[0078] Claim 26 describes a measuring device for gases dissolved in liquids which is particularly simple as it does not have to be introduced directly into the sample liquid in a vessel or in a pipeline. The measuring chamber is here presented substantially as an extension in a bypass—parallel to a pipeline through which the liquid to be tested for its gas contents is flowing—wherein the closing of the measuring chamber is produced by respective valves in the bypass feed line to and discharge line from the measuring chamber. It may be advantageous with regard to this “bypass measuring chamber” arranged outside the pipeline to thermostat the said chamber. Since the measuring chamber cannot be kept at a constant temperature by the liquid medium flowing round it, results can be obtained which are even more accurate than if the sample temperature is just measured in each case and taken into consideration in the calculation.

[0079] Here again the rotor or oscillating body serving to accelerate the establishing of the equilibrium pressure in the liquid to be measured can be separated from its drive by housing the drive in its own chamber, as provided according to claim 27.

[0080] With regard to the drive of the membrane, essential to the invention for the surface shape-change and responsible for the volume change in the measuring chamber, the said drive may operate in various ways, as is implied by claim 28.

[0081] Claim 29 provides details of a type of control, preferred within the scope of the invention, of the mechanical components provided for opening and closing the measuring chamber when the sample is replaced.

[0082] Claim 30 has as its subject a mobile device for flexible use, substantially designed as a hand-operated instrument, for determining the content quantities of gases dissolved in liquids and their solubilities and/or their saturated vapour pressures, it being necessary here to stress that a simplified bypass solution, i.e. a measuring chamber according to claim 31, which merely needs to be fitted fluid-tight to a connection issuing from a pipeline through which liquid is flowing, is particularly preferred, as in a measuring chamber of this kind the sample liquid not longer goes back. into the pipeline or the vessel with the liquid after the measurement, but is discarded.

[0083] In a laboratory instrument according to the last two claims mentioned, it may also be advantageous to thermostat the measuring chamber, e.g. with a Peltier thermostat. Thus in these laboratory applications in which the measuring chamber cannot be kept at a constant temperature by means of the liquid medium flowing round it, results can be obtained which are even more accurate than if the sample temperature is just measured in each case and taken into consideration in the calculation.

[0084] The embodiment of the device according to the invention according to claim 32 is particularly precise in its method of operation and space-savingly slim in its design. In this case the end or front surface of a very precisely guidable volume-changing piston substantially takes the place of a membrane, variable in its shape, as the partial region of the inside wall of the measuring chamber provided for changing the volume of the interior space thereof, which piston, sealed by means of an inherently stable seal to the inside wall of the measuring chamber preferably designed as a hollow cylinder, is movable therein so as to slide forward and back in a linear manner. The space-saving design is achieved by the fact that the rotor or stirrer for establishing the equilibrium in the measuring chamber and the drive providing for the rotation of the stirrer by means of a magnetic coupling through the end wall of the volume-changing piston are arranged one behind the other, as it were, and coaxially with the measuring chamber housing and with the said measuring chamber. An important feature is also the mechanical control of the valves, operable by the volume-changing piston or upon the movement thereof, for supplying liquid for measuring into the measuring chamber and removing it therefrom after the completion of each measuring cycle.

[0085] An embodiment according to claim 33 is especially preferred—particularly with regard to maintaining a pressure of the sample liquid above the saturated vapour pressure thereof to prevent bubble formation therein in the measuring chamber when the sample liquid is replaced between two measuring cycles or when the measuring chamber is filled before a new measuring cycle.

[0086] As far as the advantages of the new devices or device variants for analysing gases dissolved in liquids contained in claims 15 to 33 are concerned, the following important points should be particularly emphasised:

[0087] The sample replacement and the establishing of the equilibrium pressure are able to take place quickly, extrapolation of the equilibrium pressure is not necessary, with the result that very short measuring cycles with very high measuring accuracy are achieved.

[0088] The parts of the measuring chamber in contact with the sample may be designed so as to be smooth, self-emptying and without constrictions hindering automatic cleaning, so that the best hygiene preconditions for using these measuring devices in foodstuff production are provided.

[0089] The number of moving parts and seals in the measuring devices is minimized, enabling lower production costs, high failure safety and long maintenance intervals to be achieved.

[0090] The devices according to the invention may be used for the greatest variety of applications and may be designed to comply with the particular requirements of each:

[0091] For use directly on a production line, thus on a pipeline in a beverage filling operation, for example, it may be designed as an “inline instrument” which is flanged to the product line or to a product tank.

[0092] For use in a bypass configuration, a bypass instrument may easily be provided.

[0093] For the measurement on beverage casks and for spot-measurement on production lines, the new device may be designed as a portable, battery- and/or mains-operated laboratory instrument, which may either be connected via hoses to the production line or with the aid of an appropriate filling means may be filled with the sample for measuring originating from a beverage cask in such a way that the content of dissolved gases in the sample liquid is not changed during filling, so that the measurement results remain unadulterated.

[0094] The device according to the invention in its variations differs substantially from instruments of the prior art known hitherto not only in that with the said device the “two-step method” according to the invention for analysing more than one gas dissolved in a liquid can easily be achieved, and optionally fully automatically if required, but also in the features which are advantageous when used in the method known per se with the purely “single expansion” of the measuring chamber volume. It can therefore be used both in accordance with the known method and also in particular in the various embodiments of the method according to the invention described above.

[0095] The invention is explained in detail with the aid of the drawing:

[0096]FIG. 1 shows an analyser according to the invention on the single chamber principle,

[0097]FIG. 2 shows an alternative embodiment on the single chamber principle,

[0098]FIG. 3 shows a new analyser designed as a bypass instrument, all these Figures being sectional views, and the diagram in

[0099]FIG. 4 shows a part-sectional oblique view of the measuring chamber volume increase membrane.

[0100]FIGS. 5 and 6, finally, show respective sectional views of another, particularly preferred embodiment of the new analyser as a bypass instrument, in two different operating positions.

[0101] The embodiment of the new analyser instrument 1 shown in FIG. 1 is formed with a housing connection 210 penetrating the wall 101 of a pipe 100 or vessel containing the liquid 10 for analysis and projecting into the sample liquid 10, the said connection ending—upwardly in the drawing—with an annular edge 212 within which is arranged or stretched a membrane 7 made of an elastomeric material which adjoins the said edge fluid-tight and is located in a plane-surface basic geometry G0. This membrane 7 may be changed in its surface shape or surface geometry in a defined manner and to a precisely predeterminable degree in each case by means of a rod-like or hollow cylinder-shape membrane driver 8, or several such drivers 8, secured to the said membrane, by the movement thereof towards the exterior—or downwardly in FIG. 1.

[0102] In FIG. 1 two positions G1 and G2 of the membrane 7 are shown by a broken line, these positions corresponding to two defined surface geometries, other than the basic geometry G0, and chamber volume increases thereof.

[0103] Guided through the membrane 7, fluid-tight, is a hollow piston rod 3, by means of which a piston head 220 having a cavity 225 is movable upwardly in the direction away from the membrane 7, or in reverse. The piston 220 has an approximately flat cylinder-shape recess 201 directed towards the membrane 7 of the housing connection 210 and fully open towards the said membrane, the annular edge 222 of the said recess bearing a sealing ring 223 extending around it.

[0104] Into the said recess 201 with its non-changeable interior wall 22 project the sensor parts or sensor surfaces of a pressure sensor 4 and a temperature sensor 5 proceeding from the piston cavity 225 and penetrating the partition 226 thereof separating it from the recess 201. The measured value transfer lines 40 and 50 of the said sensors are guided, as is the power supply line 60 for the stirring element drive 61, out of the piston cavity 225 through the piston rod 3 to the exterior.

[0105] The analyser 1 according to the invention is shown in FIG. 1 in a closed position enclosing the sample liquid 10 so as to effect a fluid-seal by means of the annular seal 223. In this closed position a measuring chamber 2 is formed with an interior space 20 having a defined standard measuring chamber volume, in which is located an oscillating element 62 operable in a non-contact manner by the aforementioned magnet-operated drive 61 in the piston cavity 225 to accelerate the establishing of equilibrium pressure.

[0106] In the measuring chamber 2 just defined, the membrane 7 forms a shape-variable region 21 of the wall of the chamber interior space, which may be converted in its shape or surface geometry from the basic geometry G0 into other surface shapes G1 or G2, the non-variable region 22 thereof being defined substantially by the internal wan of the recess 201.

[0107] When the surface geometry thereof is changed to the two geometries G1 and G2, for example, there occurs a first, smaller, increase in the volume of the measuring chamber interior space 20 and then a second, larger, such measuring chamber interior space volume increase.

[0108] After each of these volume increases—after appropriate cavitation-generating stirring by means of the oscillator 62, operable in a non-contact manner by means of the magnet-operated drive 61, to accelerate the establishing of the equilibrium pressure in the measuring chamber 2—as well as the temperature ascertained by means of the temperature-measuring probe 5, the equilibrium pressure establishing in the measuring chamber 2 is ascertained by means of the pressure-measuring probe 4. The measured pressure values obtained in this way form the basis for ascertaining the content quantities of dissolved gases in the sample liquid 10 and also the solubility (solubilities) and/or said vapour pressure(s) thereof.

[0109] When the pressure measurements in the chamber 2 after at least two volume increases are completed, the piston 220 is moved—upwardly in the drawing—by means of the piston rod 3 and because of the creation of a slit-type opening 30 extending around between the edges 212 and 222, or the sealing body 223 located there, opening of the measuring chamber 2 to its fall extent results, bringing about the rapid and effective removal of the sample liquid 10 previously located therein and subjected to the volume increase steps, and the filling up thereof with the liquid 10 surrounding the measuring chamber 2, so that a new measuring cycle can be stared very quickly.

[0110] To sum up and to explain in detail, the following should be emphasised:

[0111] The measuring chamber 2 is designed in the manner of a self-emptying box projecting into the liquid for measuring and with the said liquid circulating around it, the said box preferably being oriented not horizontally—as shown in the Figure—but vertically, which accelerates the flushing process even more.

[0112] The size of the opening gap 30 is such and the shape of the recess 201 of the measuring chamber 2 is designed such that the liquid sample for measurement is replaced in a very short time without any other assistance.

[0113] The piston rod 3 is guided in a leakage-free manner through the membrane 7 towards the exterior to a drive.

[0114] The membrane 7 may be resiliently extended additionally in a defined manner by means of a driver.(drivers) 8, with the measuring chamber 2 closed, and may thus be changed in its surface geometry, thereby increasing the measuring chamber volume.

[0115] At the beginning of each measuring cycle, the measuring chamber 2 is opened by mea of the piston rod 3. The sample liquid 10 in the measuring chamber 2 is replaced. The measuring chamber 2 is then scaled tight by withdrawing the piston rod 3.

[0116] The membrane 7 is extended by means of the membrane driver 8, by which the measuring chamber volume is increased and the sample liquid 10 in the measuring chamber 2 is expanded. The volume increase of the measuring chamber 2 may be set at a level such that any other dissolved gases present in the sample have only a minimal effect on the content thereafter to be determined in the liquid of a gas forming the main component, such as carbon dioxide.

[0117] The establishing of the equilibrium pressure inside the measuring chamber 2 is promoted by means of an oscillating body 62 whose rapid movement in the sample liquid 10 produces cavitation.

[0118] Alternatively, the degassing device for establishing the equilibrium pressure may consist of an ultrasonic transducer whose ultrasonic energy emitted therein is regulated such that the equilibrium pressure establishes quickly. The equilibrium pressure and the temperature are measured and from these the carbon dioxide content is calculated. Thereafter the membrane 7 is relaxed and by means of the piston rod 3 the measuring chamber 2 is opened.

[0119] In the gas content measuring device 1 shown in FIG. 1, according to the method in accordance with the invention, after a first determination of the equilibrium pressure and the temperature following a first volume increase in the chamber 2, by means of a second, further, extension of the membrane 7 by means of the driver 8 the measuring chamber volume is further increased, the degassing device 61, 62 is activated again and thereafter the changed equilibrium pressure newly establishing is determined. This process may also be run through several times.

[0120] Because of the effect of the differing solubilities of the gases dissolved in the sample liquid, from the measured equilibrium pressures it is possible, for instance, to eliminate the influence of the other dissolved gases on the ascertained carbon dioxide content by calculation and/or to determine the contents of the other dissolved gases, in particular oxygen and nitrogen, and the gas solubilities thereof as well.

[0121] According to an embodiment of the device according to the invention which is entirely analogous with regard to its structure, two or more measuring chambers 2 as just described, operated in parallel, may serve as measuring devices; in this case differing volume increases are implemented in each of the measuring chambers by means of differing changes of the shape of their membranes 7.

[0122] The separate pressure-measuring sensors 4 in multiple chambers of this kind are advantageously identical in design and the membranes 7 are adjustable to defined volume increases which differ from one another in each case. With the aid of the differing equilibrium pressures then determined simultaneously in the measuring chambers 2, the effect of other dissolved gases, e.g. on the calculated carbon dioxide content, is eliminated by calculation, and/or the content quantities of the other dissolved gases and the gas solubilities and also saturated vapour pressures can be determined as well.

[0123] In some—mostly more difficult—cases, it may also be advantageous to combine the device according to the invention with other sensors, preferably selective gas sensors, and to include their measured values in the result calculation based on the measured equilibrium pressure values.

[0124]FIG. 2 shows another embodiment of the invention—with reference numeral meanings otherwise unchanged or used analogously—which is particularly suitable for installation in pipelines. The piston rod 3 for opening and closing the measuring chamber 2 is in this case guided through the pipe wall 101 in a leakage-free manner via a membrane 70. Located in the hollow piston rod 3 is the membrane driver 8 which extends the membrane 7—the said membrane here sealing off the piston 220 from the sample liquid 10 so as to effect a fluid-seal—by means of whose shape change the measuring chamber volume can be increased with the measuring chamber 2 closed.

[0125] In this embodiment according to FIG. 2 similar conditions substantially prevail as in the measuring device 1 according to FIG. 1, but here the recess 201 essential for forming the measuring chamber 2 or the interior space 20 thereof is arranged with its boundary wall region 22, which remains constant, in a housing connection 210 penetrating the wall 101 of the pipe 100 diametrically to the passage-through of the piston rod 3.

[0126] The connection 210 has a cavity 225—here open upwardly or towards the exterior—which is separated from the recess 201 by the partition 226. Located in the said cavity are the measurement sensors 4, 5 for pressure and temperature which penetrate the partition 226 in a fluid-tight manner and whose actual sensor heads are in contact with the sample liquid 10 in the recess 201 or chamber 2, and also the non-contact magnet-operated drive 61 for the oscillating body 62.

[0127] When the membrane 7 forming the shape-variable region 21 of the measuring chamber boundary is moved upwardly with the piston 220, moved up by means of the piston rod 3 by the drive 94 monitored by the control and calculation unit 92—the said unit being adjustable from the input and display unit 91—the recess 201 with the sample liquid 10 located therein is closed fluid-tight and thus the measuring chamber 2 is formed with a precisely defined volume of the interior space 20.

[0128] Then, controlled by the control and calculation unit 92 on the basis of the parameters input via the input and display unit 91, there occur the volume increase steps and also the establishing of the equilibrium pressure, preferably accelerated by means of the oscillating body 62 operated in a non-contact manner by the magnet-operated drive 61 in the housing connection space 225, thereafter the pressure and temperature measurement by means of the respective sensors 4 and 5, the measurement data of which are issued via the data lines 40 and 50 to the control and calculation unit 92 where, using an algorithm, as explained by way of example in the descriptive section, or one analogous thereto, they are converted into the required values of the content quantities of the dissolved gases, from the solubilities and/or saturated vapour pressures thereof, and are passed to the input and display device 91 or alternatively straight to a control unit for the production line, i.e. a beverage production line, for example.

[0129]FIG. 3 shows—with otherwise analogous reference numeral meanings—a device according to the invention in the preferred embodiment as a bypass instrument. For practical reasons this is not directly fitted into the equipment, e.g. a pipeline 100, which contains the liquid 10 to be measured, but instead a partial flow of the liquid 10 to be analysed is diverted from this equipment and supplied to the bypass instrument 1 where the measurement takes place. This partial flow is then returned or possibly discarded.

[0130] The feed and through-flow of the liquid 10 is achieved by opening the valves 115 and 116 located in the bypass feed line 111 and in the discharge line 112, whereby a previous liquid sample is flushed out.

[0131] Located in the measuring chamber 2 is a pressure sensor and a temperature sensor 4, 5, a degassing device 61, 62 provided according to the invention and the resilient membrane 7 provided for a specific measuring chamber volume increase and forming the shape-variable part 21 of the boundary wall of the measuring chamber interior space. After the closing of the valves 115, 116, or of the measuring chamber 2, the membrane 7 is extended by means of the drive 93 and the driver 8 and the measuring chamber volume is thereby increased. The degassing device 61, 62 provided according to the invention steps into action and accelerates the establishing of the equilibrium pressure. The equilibrium pressure and the temperature are measured and from these the control and calculation unit 92 is able to calculate the content quantity (quantities) of dissolved gases, i.e. the carbon dioxide content, for example, of the liquid 10 for analysis.

[0132] According to the preferred embodiment of the invention, after the first volume increase and determining of the equilibrium pressure and the temperature, the mea chamber volume is further increased, the degassing device 61, 62 is again activated and thereafter the newly establishing, now changed equilibrium pressure is again determined. This process can of course also be run through several times.

[0133] As a result of the effect of the differing solubilities of the gases dissolved in the sample liquid, it is possible from the measured values of the equilibrium pressures to eliminate the effect of the “other” dissolved gases, e.g. on the ascertained carbon dioxide content, by calculation and/or to determine the content quantities of the “other” dissolved gases, e.g. oxygen and nitrogen, and their solubilities in the sample liquid as well.

[0134] In this embodiment of the device according to the invention also, two or more bypass measuring chambers 2 may be used, operated in parallel and preferably equipped in the same way, the volume increases applied, in accordance with the method according to the invention, being adjusted in each of these measuring chambers to differing, respectively defined values.

[0135] With the aid of the differing equilibrium pressures determined simultaneously in the measuring chambers 2, the effect of the other dissolved gases on the calculated carbon dioxide content may be eliminated by calculation and/or the content of the other dissolved gases and/or their gas solubilities and/or saturated vapour pressures may be determined as well.

[0136] Here too it may be advantageous to combine the device according to the invention with other sensors, preferably selective gas sensors, which may also be located entirely outside the measuring chamber, and to include the measured values delivered by the said sensors in the result calculation.

[0137] With regard to the technical implementation itself, it should be emphasised quite generally at this point that the measuring device to be introduced into the liquid for measuring is advantageously equipped with connections or flanges which may be fitted to existing, normal industry-practice, standard connections or flanges or fittings of the vessels containing the liquid, tanks, or pipelines through which the said liquid is flowing.

[0138] A device according to the invention for measuring the content quantities of dissolved gases on beverage casks and for spot-measurement on production lines or tanks may also be designed as a portable, battery- and/or mains-operated laboratory instrument. This may either be attached to the production line 100 or to a product tank via hoses or may be filled from casks by means of a manual or automatic filling device.

[0139] A mobile analyser instrument of this kind is represented in schematic form within the scope of FIG. 3, the said instrument being attachable to a pipe connection 111, branching off the pipe 100 through which the liquid 10 is flowing and comprising a valve 115, e.g. by means of a pipe connection with a fluid-tight screw connection 150 or by means of a pressure-resistant hose via its feed line 111′: apart from the aforementioned connection 150 it has the same structure as the fixedly attached bypass instrument described above. Advantageously, however, there is no return into the main liquid stream provided, but there is an outlet pipe 112′, closable for the measurement by means of a valve 116′—illustrated in this particular case by a broken line—by means of which the sample liquid 10 may be disposed of after the measurements have taken place.

[0140] The membrane 7 shown in FIG. 4 and variable in its surface geometry forms the part 21 of the boundary wall of the measuring chamber which is variable in its shape. This membrane 7 is made of a relatively thick (e.g. 5 mm) heavy-duty elastomeric material, such as Perbunan, for example, and has on its side directed towards the measuring chamber interior space an adhesion-reducing, hydrophobic coating 71 made of Teflon, for example.

[0141] On its outside periphery the said membrane is held by a fixed membrane stop or membrane supporting ring 271 joined to the measuring chamber housing, for example, or is clamped therein.

[0142] Centrally the membrane 7 has an opening 701 which is penetrated by the piston rod 3, as shown in FIG. 1, for the movement of the piston head 220 shown therein, comprising the recess 201—there forming the non-variable part of the measuring chamber 2.

[0143] The inside edge of the elastomeric membrane 7 encircling this passage opening 701 is joined to a membrane-supporting ring 272 which supports or holds the said membrane at that location, is joined to the piston rod 3 and, with the measuring chamber closed, is therefore stationary and specifically positioned.

[0144] Vulcanised into the membrane 7 is the thickened edge 81 of a securing ring 80, projecting from the underside of the membrane 7, which is joined, for instance, to a hollow operating rod 8 designed to cooperate with the downwardly protruding part 82 of the ring 80, or to a hollow cylinder of that kind, which rod or cylinder is joined to the membrane-operating drive 93 provided for defined shape-changing of the membrane 7 and shown in FIG. 2, for instance. The membrane 7 may be flat for example, in the basic position shown in FIG. 4 corresponding to the standard volume of the measuring chamber, and as the membrane-operating hollow cylinder 8 moves downwardly to effect a desired increase in the interior space volume of the measuring chamber, it then forms a sort of circularly closed, flat-V-shape valley.

[0145] Also indicated in FIG. 4 is how the membrane 7 or the inside and outside edge regions thereof are provided at that location with meander-shape or toothed reinforcing structures 704, 705 joined to the said membrane or supporting it, which structures serve to ensure the geometrically true shape and also the defined shape change of the membrane 7 supported over a large area thereon even after a large number of measurements with volume increase steps.

[0146]FIGS. 5 and 6 show—with reference numeral meanings otherwise unchanged—sections through another, particularly preferred embodiment of the new measuring device 1 comprising a measuring chamber 2, wherein the front surface 701 of a hollow volume-changing piston 70 is substantially provided as the movable wall region 21 changing the volume of the interior space 20 of the measuring chamber 2, the said piston being movable so as to slide in a linear manner in the interior or cavity 200 of the housing 250 accommodating the measuring chamber 2.

[0147]FIG. 5 shows the measuring chamber 2 in the state of having the maximum interior space volume, in which the volume-changing piston 70 occupies a “bottommost” position Vmax, and the valve bodies 1151, 1152, acted upon with the force of respective springs, of the inlet valve 115 in the feed line 111 of the measuring bypass and the outlet valve 116 in the discharge line 112 of the bypass, the said bypass being connectible or connected to a pipeline—not shown—with the sample liquid 10 to be tested for its gas content flowing through the said pipeline, are seated in their valve seats so as to effect a fluid-seal, and thus both valves 115, 116 are held closed.

[0148] The volume-changing piston 70 is sealed, by means of an inherently stable sealing ring 703 preferably made of an inert material such as Teflon in particular, against the inside wall of the housing cavity 200, or the measuring chamber 2, so as to effect a sliding seal. The drive of the volume-changing piston 70 is effected by means of a motor 93 with a linear-, more particularly spindle drive 793, which motor is controlled from the control and calculation unit 92 and is arranged in the cavity 200 of the housing 250 in line with the housing axis.

[0149] Located in the interior or cavity 700 of the piston 70 is a stirrer drive motor 61—again arranged in line with the axis a of the housing 250—with a disc-type magnetic body 611, the magnets thereof—acting through the end wall 702 of the volume-changing piston 70—being magnetic force-coupled with the magnets of the similarly disc-type magnetic body 621 of a rotor or stirrer 62 arranged in the measuring chamber 2, or in the interior space 20 thereof, again in line with the housing axis. The rotor or stirrer arms or blades 626 are arranged on a hollow stirrer shaft 625, projecting upwardly from the magnetic body 621, at a distance away from the magnetic body 621.

[0150] Two valve control rods 715 and 716 project upwardly from the end wall 702 or out of the end surface 701 of the volume-changing piston 70 parallel to or in line with the housing axis a, the control rod 716 passing through the hollow stirrer 62.

[0151] In the illustrated end position Vmax of the volume-changing piston 70—which corresponds to the maximum volume of the interior space 20 of the measuring chamber 2 adjustable in the said measuring chamber—the ends of the two valve control rods 715, 716 are located relatively fir away from the spring-loaded valve bodies 1151, 1161—here in the form of ball valves—of the sample liquid inlet valve 115 located in the feed line 111 opening into the measuring chamber 2 for the sample liquid 10 to be tested for its content of dissolved gases, and of the outlet valve 116 located in the discharge line 112—leading out of the measuring chamber 2.

[0152] The distance d2 marked in FIG. 5 between the free end of the valve control rod 716 and the valve body 1161 of the outlet valve 116 is slightly smaller than the maximum clearance of the movement of the volume-changing piston 70, whose task is to be available for the step by increase of the volume of the measuring chamber interior space 20 provided during the individual measurements in the course of a measuring cycle.

[0153] The distances d1 and d2 between the ends of the valve control rods 715 and 716 and the valve bodies 1151 and 1161 are advantageously such that, after the opening of the valves 115 and 116 when the measuring chamber 2 is filled with fresh sample liquid 10 before the commencement of a measuring cycle, as the volume-changing piston 70 moves away from the valves 115 and 116, i.e. when the in- and outflow 111, 112 of sample liquid 10 into or out of the measuring chamber 2 is stopped, the outlet valve 116 is closed earlier than the inlet valve 115.

[0154] Also to be inferred from FIG. 5—indicated by means of a constriction of the discharge line 112—is a pressure-reducing element 1121, or pressure-reducing valve, which serves to adjust the throughflow of the sample liquid, more particularly when the said sample liquid is replaced, such that the pressure of the sample liquid 10 does not fall below the saturated vapour pressure thereof during filling, so ensuring gas bubble-free filling of the measuring chamber 2.

[0155]FIG. 6 shows—with reference numeral meanings fully analogous to FIG. 5—the state of the new measuring device 1 during replacement of the sample liquid 10 to be tested for its gas content after completion of one measuring cycle and before the commencement of a new measuring cycle.

[0156] Here, the volume-changing piston 70 is located in an “upper” end position Vmin, in which the variable volume of the interior space 20 of the measuring chamber 2 is at its smallest. The two valve control rods 715, 716 have in this case lifted the valve bodies 1151 and 1161, against the force of the valve springs thereof, off the seats of the valves 115 and 116, so that the previously tested sample liquid 10 is able to flow out of the measuring chamber 2 and fresh sample liquid is able to flow in. As already stated above, by means of a pressure-reducing element or restrictor 1121 in the discharge line 112, the pressure in the sample liquid 10 may be kept at a pressure above the saturated vapour pressure thereof, and in this way the formation of bubbles of the dissolved gas is prevented. 

1. A method for determining the quantities of at least two, and optionally also the solubility or saturated vapour pressure of at least one, of a plurality of gases, for instance carbon dioxide, nitrogen and/or oxygen, contained or dissolved in a liquid, preferably a beverage, which gases differ from one another in their solubilities and/or in their saturated vapour pressures, comprising: completely filling a measuring chamber with the liquid to be tested (the “sample liquid”), the measuring chamber being equipped with a pressure measuring sensor; closing the measuring chamber in a fluid-tight manner, thereby defining a standard measuring chamber volume; increasing the volume of the measuring chamber in a number of steps corresponding at least to the number of gases whose quantities are to be determined, by volume increase factors which, related to the standard volume, differ from one another; after each of the volume increase steps, ascertaining the equilibrium pressure then established in the measuring chamber; and on the basis of the pressures so ascertained, calculating the quantities of at least two of the gases and also optionally the solubility and/or the saturated vapour pressure of at least one of the gases.
 2. A method according to claim 1, characterised in that the volume of the measuring chamber(s) filled with the sample liquid is increased, starting from the standard volume thereof, in each volume increase step in each case by a volume increase factor ranging from 1.005 to 1.75, preferably 1.01 to 1.50, more particularly 1.03 to 1.10.
 3. A method according to claim 1 or 2, characterised in that by means of a temperature-measuring sensor arranged in the measuring chamber the temperature of the sample liquid is ascertained, and the measured temperature value(s) thus obtained is or are included in the calculation of the content quantities of the individual gases dissolved in the liquid, and optionally also of the solubilities and/or saturated vapour pressures of the individual gases in the said liquid.
 4. A method according to one of claims 1 to 3, characterised in that the defined measuring chamber volume increase steps which differ from one another are implemented in chronological succession, or sequentially, in one and the same measuring chamber filled with the sample liquid, in that after each of these steps the equilibrium pressure establishing in the measuring chamber is ascertained and the measured pressure values obtained in this way are used to calculate the content quantities, and optionally the solubilities and/or saturated vapour pressures, of the individual gases contained in the sample liquid and are connected to one another via an algorithm.
 5. A method according to one of claims 1 to 3, characterised in that at least two of the measuring chamber volume increase steps which differ from one another are implemented—preferably simultaneously—in each of at least two measuring chambers each filled with the sample liquid, end in that thereafter the equilibrium pressure respectively establishing in each of the measuring chambers is ascertained, whereupon the measured pressure values obtained in this way are used to calculate the content quantities, and optionally the solubilities and/or the saturated vapour pressures, of the individual gases dissolved in the sample liquid and are connected to one another via an algorithm.
 6. A method according to one of claims 1 to 4, characterised in that—in the case in which a single measuring chamber is used—the defined measuring chamber volume increase steps taking place in chronological succession are each implemented with volume increase factors increasing with each step.
 7. A method according to one of claims 1 to 6, characterised in that the measuring chamber volume is increased—in each case relative to a standard measuring chamber volume—at least or only in as many volume increase steps as there are gases dissolved in the liquid having a solubility or content quantity of these gases in the liquid which is not to be disregarded, and/or in that by means of volume increase steps with increased volume increase factors, preferably with such factors of at least 1.15, the effect of the gases to be disregarded because of their low solubility or content quantity is kept below the desired analysis accuracy.
 8. A method according to one of claims 1 to 7, characterised in that in the case in which CO₂ is dissolved in the sample liquid as the main component, the gases oxygen and nitrogen dissolved therein in substantially smaller quantities are treated as a unified double gas component with a mean or weighted solubility.
 9. A method according to one of claims 1 to 8, characterised in that each step-by-step measuring chamber volume increase is implemented by means of defined extension of and thus changing of the surface shape or surface geometry of a membrane forming a partial region of the boundary or wall of the measuring chamber interior space.
 10. A method according to one of claims 1 to 9, characterised in that measured values ascertained by at least one sensor in addition to the pressure-measuring sensor and the optionally provided temperature-measuring sensor, preferably by means of a selective gas sensor, fitted in the measuring chamber or in contact with the sample liquid externally thereof, are included as well in the calculation of the content quantities of the individual gases contained or dissolved in the sample liquid, and optionally also of the solubilities and/or saturated vapour pressures of the individual gases in the sample liquid.
 11. A method according to one of claims 1 to 10, characterised in that—in order to accelerate the establishing of the equilibrium pressure in the measuring chamber filled with the sample liquid, preferably immediately after a chamber volume increase step—the sample liquid is set in a state of movement more particularly an oscillating, rotational and/or vortex movement, generating cavitation in the said liquid.
 12. A method according to one of claims 1 to 11, characterised in that accelerated establishing of the equilibrium pressure in the measuring chamber is brought about by means of (oscillating) movement and/or rotation of an oscillating body, rotor, in the sample liquid, optionally operated via a non-contact, more particularly magnetic, coupling.
 13. A method according to one of claims 1 to 12, characterised in that accelerated establishing of the equilibrium pressure in the measuring chamber is preferably implemented by cavitation by means of an ultrasonic transducer equipped with a regulating device for the power introduced into the sample liquid.
 14. A method according to claim 13, characterised in that the change over time of the pressure measured in the measuring chamber after the ultrasonic transducer has been switched off is used as regulating variable for the ultrasonic power to be introduced into the sample liquid.
 15. A device for determining the content quantity (quantities) and/or solubility (solubilities) and/or saturated vapour pressure(s) of at least one gas dissolved in a liquid, preferably a beverage, more particularly for the implementation of the analysis method according to one of claims 1 to 14, characterised in that it has a fluid-tight measuring chamber (2) which may be filled completely with the sample liquid (10) and closed fluid-tight, comprising at least one partial region (21) of the boundary or wall of its interior space, which partial region is provided for changing the volume of the interior space (20) thereof, is variable in its position and/or surface geometry—while fully retaining the fluid-tightness—and is preferably formed by a membrane (7), which partial region—staring from a standard position and/or standard geometry (G0)—is movable into, and/or deformable to, at least one defined location position and/or surface geometry (G1, G2)—producing an increase in the volume of the measuring chamber interior space corresponding in each case to a freely selectable and adjustable volume increase factor.
 16. A device according to claim 15, characterised in that—in order selectively to determine the content quantities and/or solubilities and/or saturated vapour pressures of at least two gases dissolved in a liquid, preferably a beverage—the partial region (21) of the interior space boundary or wall of the measuring chamber (2) which is variable in its position and/or surface geometry and is preferably formed by a membrane (7), is movable into, and/or deformable to, at least two mutually differing defined location positions and/or surface geometries¹ (G1, G2)—producing increases in the volume of the measuring chamber interior space corresponding in each case to a freely selectable and adjustable volume increase factor. ¹ ‘Flächengeometrie(n)’ in the source text, i.e. ‘surface geometry (geometries)’.
 17. A device for determining the content quantity (quantities) and/or solubility (solubilities) of at least one gas dissolved in a liquid, preferably a beverage, more particularly for the implementation of the analysis method according to one of claims 1 to 14, characterised in that it has at least two measuring chambers (2), preferably of identical design, adapted for filling completely with the sample liquid and closable fluid-tight, each comprising at least one partial region (21) of the boundary or wall of its respective interior space, which partial region is provided in each case for changing the volume of the interior space (20) thereof, is variable in its position and/or surface geometry while fully retaining the fluid-tightness, and is preferably formed by a membrane (7), each of which partial regions is movable into, and/or deformable to, at least one defined location position and/or surface geometry respectively—producing an increase in the volume of the measuring chamber interior space corresponding in each case to a freely selectable and adjustable volume increase factor.
 18. A device according to claim 17, characterised in that—in order selectively to determine the content quantities and/or solubilities and/or saturated vapour pressures of at least two gases dissolved in a liquid, preferably a beverage—the partial regions (21) of the at least two measuring chambers (2), variable in their position and/or surface geometry and preferably formed by a membrane (7), are movable into, and/or deformable to, respective mutually differing defined location positions and/or surface geometries—producing increases in the volumes of the interior space of the measuring chambers corresponding to respective, differing volume increase factors.
 19. A device according to one of claims 15 to 18, characterised in that there is arranged in the measuring chamber (2) thereof—to assist and accelerate the establishing of the equilibrium pressure in the said chamber after a change, more particularly increase, of the interior space volume thereof—at least one motion-generating element (61, 62) which sets the sample liquid in motion or cavitation, preferably a rotor or oscillating body (62) operable in a non-contact manner by a drive element (61), e.g. a magnet-operated drive.
 20. A device according to one of claims 15 to 19, characterised in that the partial region (21) of the boundary or wall of the measuring chamber interior space (20) provided for a defined increase of the interior space volume of the measuring chamber (2) and preferably formed by at least one membrane (7), is variable in a defined manner in its location position and/or surface geometry from a standard location position and/or standard surface geometry directly or indirectly, for instance through the intermediary of a transmitting medium, by a drive element (93)—controllable via a control and calculation means (92) from a device, e.g. a display (91), for the input of a measuring chamber volume increase factor desired in the particular instance and for displaying measurement data.
 21. A device according to one of claims 15 to 20, characterised in that it comprises a measuring chamber (2) projecting into the optionally flowing liquid (10) for analysis of its contents of gases dissolved therein, or adapted to be introduced under the surface thereof or located there, or projecting into a vessel containing the liquid (10) or into a pipeline (100) through which the liquid is flowing, the said measuring chamber comprising an interior space (20) defined by its boundary or wall, of which a partial region (21) is formed with a membrane (7) which is variable in its surface geometry in a reproducibly defined manner by means of at least one membrane driver (8) connected to a drive element (93) or coupled thereto and which closes off on the liquid side a housing connection (210) which penetrates the wall (101) of a vessel or pipe (100) in a fluid-tight manner, and the other or remaining partial region (22) of which is formed substantially by the inside surface of a recess (201) which is open towards the said membrane (7), has on its edge (222) a preferably ring-shaped sealing body (223), and more particularly is the shape of a flat cylinder or flat indentation, for holding the sample liquid (10), wherein the said recess (201) is formed on a housing piston (220) which is movable by means of a piston rod (3) penetrating the membrane (7) in a fluid-tight manner to open the measuring chamber interior space (20) and to fill the said interior space with the sample liquid (10) away from the said membrane (7), and thereby frees a slit-type opening (30) preferably extending around between the housing connection (210) with the membrane (7), or the edge (212) thereof, and the said sealing body (223), and back in the direction towards the said membrane (7) to enclose the sample liquid (10) in the measuring chamber interior space (20) in a fluid-tight manner.
 22. A device according to claim 21, characterised in that the housing piston (220) itself has a fluid-tight cavity (225), separated from the recess (201), in which there is arranged a drive element, more particularly a magnet-operated induction drive element (61), for at least one oscillating and/or rotational body (62) arranged in the measuring chamber interior space (20) for accelerating the establishing of equilibrium pressure in the measuring chamber (2) filled with the sample liquid (10).
 23. A device according to claim 21 or 22, characterised in that into the partition (226) between the measuring chamber recess (201) and the cavity (225) of the housing piston (220) are fitted a pressure-measuring sensor (4) extending into the measuring chamber (20) [sic] or in contact with the sample liquid (10) enclosed therein, and preferably a temperature-measuring sensor (5) of the same kind.
 24. A device according to one of claims 21 to 23, characterised in that the measurement data lines (40, 50) of the sensors (4, 5) and the power supply- and control lines (60) for the oscillating or rotational body drive element (61) are guided through the cavity (225) of the housing piston (220) and trough the interior space or through a cavity of the piston rod (3) thereof to the exterior.
 25. A device according to one of claims 15 to 20, characterised in that a partial region (22) of the boundary wall of the measuring chamber (2) to be filled with the liquid (10) for analysis for its content of dissolved gases, or of the interior space (20) thereof, is formed by a recess (201) of a pipe or housing connection (210) penetrating a pipe- or vessel wall (101) in a fluid-tight manner and closed off towards the exterior by a partition (226) or the like, which recess is open to the said liquid (10) when the chamber (2) is filled and has a preferably ring-like sealing body (223) on its edges (222), and preferably has the shape of a flat cylinder or flat indentation, whilst the remaining partial region (22) of the measuring chamber interior space wall or boundary is formed by a membrane (7) directed towards the said recess (201) of the connection (210) and variable in its surface geometry by means of a membrane driver (8), which membrane (7) on the liquid side seals a hollow housing piston (220) which is movable—by means of a similarly hollow piston rod (3) guided through a fluid-sealing passage, similarly formed with a membrane (70), in the vessel- or pipe wall (101), (FIG. 2), which housing piston (220) with the membrane (7) is designed so as to be movable away from the said recess (201) of the connection (210) to open and fill the measuring chamber (2), and to free a slit-type opening (30) extending around between the sealing body (223) of the housing connection (210) and the edge (22) of the housing piston (220) sealed by the said membrane (7), and to be movable back in the direction towards the said recess (201) of the connection (210) to close the measuring chamber (2).
 26. A device according to one of claims 15 to 20, characterised in that the measuring chamber (2) is designed an extension—optionally equipped with a thermostatting device—of a bypass line (110)—branching off a pipeline (100) through which the liquid (1) for analysis is flowing and leading back thereto—with preferably simultaneously closable closing elements, more particularly valves (115, 116), in the feed line (111).to the measuring chamber (2) and in the discharge line (112) thereof, wherein a partial region (21) of the boundary or wall of the interior space (20) of the measuring chamber (2) designed in this way is formed by a membrane (7) which is variable in its surface geometry in a defined manner by means of a membrane driver (8).
 27. A device according to claim 25 or 26, characterised in that the drive element, preferably a magnet-operated induction drive element (61), is arranged in a space or cavity (225) separated from the measuring chamber (2) by a partition (226), for the oscillating and/or rotor body (62), located in the measuring chamber (2), for establishing the equilibrium pressure.
 28. A device according to one of claims 15 to 27, characterised in that the membrane driver (8) provided for changing the surface geometry of the membrane (7) of the measuring chamber (2) is coupled or connected, preferably mechanically or hydraulically, to the drive element (93), preferably a stepping motor or a pneumatic drive, which drive element is controllable via a control and calculation device (92) from an input and display device, e.g. a display (91), for the input of a volume increase factor desired in the particular instance.
 29. A device according to one of claims 15 to 28, characterised in that the movable housing piston (220) provided for opening and closing the measuring chamber (2), or the piston rod (3) thereof, or alternatively the closing elements, more particularly valves (115, 116), provided for these procedures, in the feed and return line (111, 112) of a bypass line (110) of a pipeline (101) through which the liquid (10) containing the dissolved gases is flowing, is coupled or connected, preferably mechanically or hydraulically, to the optionally pneumatic measuring chamber drive element (94)—controllable via the control and calculation device (92) from an input and display device, e.g. a display (91), for the input of a flushing time, equilibrium pressure establishing time, desired in the particular instance.
 30. A device according to one of claims 15 to 29, characterised in that it is constructed in an analogous manner to one of the embodiments disclosed in the said claims but as a hand-operated analyser instrument equipped with an input-and display- and also control- and calculation device (91, 92) and a drive element (93) fed by a power store for the measuring chamber volume change, the said instrument being adapted for introducing into a liquid (10) for analysis of its content of dissolved gases, and having the approximate form of a dip-stick, or preferably as a hand-operated analyser instrument attachable externally by means of a bypass circuit to a pipeline (100) through which the sample liquid (10) is flowing, and preferably equipped with a thermostatting device.
 31. A device according to claim 30, characterised in that it has² a measuring chamber (2) with a feed line (111′) connectible fluid-tight to a branch connection or a branch pipe (111) of a pipeline (100) through which the liquid (10) for analysis is flowing, and a liquid outlet (112′) open at the end or equipped with an outflow hose or the like and comprising a closing valve (116′). ² The claim cannot be translated as it stands in the source text. It has been translated as if ‘sie’ [it, i.e. the device] is followed by ‘aufweist’ [has] instead of ‘gebildet ist’ [is formed—in the last line of the claim].
 32. A device according to one of claims 15 to 31, characterised in that the measuring chamber (2) equipped with a feed line (111) opening into it for the sample liquid (10) and comprising a stop valve (115), and a discharge line (112) exiting therefrom and comprising a stop valve (116) is arranged in an elongated hollow-cylinder-shape housing (250) and, for changing the volume of the interior space (20) thereof, the end surface (701) of a volume-changing piston (70) is provided, the said end surface forming a partial region (21) of the wall of the measuring chamber interior space, which piston is sealed in the cavity (200) of the housing (250) against the inside wall of the said housing cavity, or of the measuring chamber (2), by means of a seal or a sealing ring (703) preferably made of Teflon, is movable so as to slide, effecting a fluid-seal, and is itself also designed so as to be hollow, which piston is movable in a linear manner via a linear- or spindle drive (793) by means of a drive motor (93) arranged in line with the axis (a) of the housing (250).and operable, controllable and regulatable from a control unit (92), in that a rotor- or stirrer drive (61) comprising a magnetic body (611) is arranged in the cavity (700) of the volume-changing piston (70) again coaxially with the axis of the housing, which magnetic body is magnetic force-coupled in a non-contact manner through the end wall (702) of the volume-changing piston (70) with the magnetic body (621) of a rotor/stirrer (62) again arranged so as to be coaxial with the housing axis and designed with stir arms (626) located at a distance from the said magnetic body (621) on a hollow stirrer shaft (625), and in that from the end surface (701) of the volume-changing piston (70) there project two valve control rods (715, 716) oriented substantially parallel to the housing axis (a), one of which may be designed so as to be coaxial with the housing axis, passing through the cavity of the stirrer (61), by means of which—in order to expel the sample liquid (10) in the measuring chamber (2) after completion of a measuring cycle out of the measuring chamber (2) by means of inflowing fresh sample liquid (10)—as the volume-changing piston (70) moves into the measuring chamber (2), substantially the valves (115, 116) of the feed and discharge line (111, 112) may be opened by the lifting of their spring force-operated valve bodies (1151, 1161) off their sealing seat, it being preferable if the distances (d1, d2) between the valve control rod (715) and the valve body (1151) of the inlet valve (115) and the valve control rod (716) and the valve body (1161) of the outlet valve (116) are dimensioned such that—when the measuring chamber (2) is filled with sample liquid (10) at the beginning of a measuring cycle—as the volume-changing piston (70) moves away from the said valves (115, 116), the outlet valve (116) is closed ahead of the inlet valve (115) in time.
 33. A device according to claim 32, characterised in that—in order to maintain a pressure of the sample liquid (10) above the saturated vapour pressure thereof to prevent bubble-formation in the said sample liquid in the measuring chamber.(2) during the replacing of the sample fluid (10) between two measuring cycles—a throughflow-regulating valve or restrictor valve or pressure-reducing valve (1121) is arranged in the discharge line (116).
 34. A method for determining the quantity or solubility or saturated vapour pressure of at least one of a plurality of gases contained or dissolved in a liquid, substantially as herein described with reference to FIG. 1 or FIG. 2 or FIG. 3 or FIGS. 5 and 6 of the accompanying drawings.
 35. A method according to claim 34, wherein the volume increase membrane is substantially as herein described with reference to FIG. 4 of the accompanying drawings.
 36. A device for determining the quantity or solubility or saturated vapour pressure of at least one of a plurality of gases contained or dissolved in a liquid, and substantially as herein described with reference to FIG. 1 or FIG. 2 or FIG. 3 or FIGS. 5 and 6 of the accompanying drawings.
 37. A device according to claim 36, wherein the volume increase membrane is substantially as herein described with reference to FIG. 4 of the accompanying drawings. 